A Practical Manual On Sea Water Distillation
With A Description Of The Necessary Machinery For The Process

194 SEA WATER DISTILLATION. 49. Assume, first, that a boiler is required for producing the above total evaporation of say 4,000 lbs. weight of steam per hour. (1) If the plant consists of a single distilling condenser and boiler only, the steam pressure of the boiler need not be very high. The total heat is nearly the same as any pressure, but being rather less at low pressure, it is ob- viously inexpedient to work at a higher steam pressure than is sufficient to let the steam pass through pipes of ordinary size. For single distillation, a maximum boiler pressure of 50 lbs. will be sufficient, say 25 to 50 lbs. pressure. The size of the boiler will have to be equal to an evaporation of 4,000 lbs. of water per hour, and Table N, on p. 197, will be a guide. (2) For double distillation also, the pressure need not be very high. Thus, say the primary steam to the evaporator has about 30 to 60 lbs. per square inch pres- sure. That would in ordinary cases be sufficient. The size of the boiler should be such as will yield of the total production. So that if 4,000 lbs. of distilled water is the required quantity per hour, the boiler must evap- orate of 4,000 lbs. = 2,222 lbs. per hour. (3) For treble distillation the boiler working pressure should be somewhat higher, say 50 to 80 lbs. The size of the boiler may be ascertained by the following Table N (p. 197), and the amount of sea water to be evaporated by the boiler will be of the total output. In the present case, therefore, of 4,000 lbs. will equal 1,666 lbs. of sea water to be evaporated by the boiler, and a suitable size of boiler may be selected from Table N. (4) For quadruple distillation the primary or boiler pressure may be 80 to 100 lbs. per square inch. The size of boiler may be settled in the same way as before,